Patent GB-361894-A (GB)
Title: Improvements in or relating to fluid pressure assisted braking mechanism
IPC: B60T13/24
Filed: 1930-08-19
Abstract: 361,894. Fluid-pressure brakes. PAYNE, M., 50, Hook Road, Surbiton, Surrey. Aug. 19, 1930, Nos. 24813 and 30574. [Class 103 (i).] Fluid-pressure brake comprises a brake pedal 1, Fig. 1, a piston 5 coupled to brake transmission through a balance lever 4 so as to react on one another and valve mechanism connected to pedal and operated to apply suction or fluid pressure to the piston whenever the pedal is moved beyond a predetermined position in the direction to apply the brakes and to interrupt the connection only when the pedal is moved towards the off position. The brake transmission 2 is connected to the middle of the lever 4. The pedal 1 is connected to the valve rod 12 which slides through a collar 13 to which the lever 4 is connected. Operation of the pedal 1 closes exhaust valve 10 further movement of which opens a valve 9 to connect the brake cylinder 6 to a source of vacuum. Wear of the brake shoes is compensated for by further movement of the piston into the cylinder and the brake pedal always moves just sufficiently to operate the valve. In a modification the pedal is extended and connected by a lost motion connection to the lever 4 below the brake transmission connection in order to enable direct pressure to be applied if the fluid pressure fails. In this construction the pedal is connected directly to the end of the lever 4 and the valve 10 and the valve 9 is closed by a spring. In a further modification the pedal is arranged to just open the valve 9 in full-applied position and the piston rod which is controlled by a pawl and ratchet does not move sufficiently to move the ratchet through the space of one tooth unless wear has occurred. A lost-motion connection between the valve and the pedal may be provided which is just taken up in full-applied position. In this arrangement full brake application is thus obtained manually. In Fig. 4 hydraulic transmission is used and the pedal 24 applies manual pressure through a piston 22 moving in a piston 21 which applies the pressure of the fluid pressure piston 30 through a lever 31 engaging projections 32 on the piston 21. Movement of the lever 24 operates the valve 27. The hydraulic pressure in the chamber 20 produced by both pistons reacts on these pistons and produces a hunting action of the valve mechanism and a proportional application between manual and fluid pressure efforts. A spring 27b closes the exhaust valve 27 and opens the suction supply valve 27a when the lever 24 is moved. If the suction supply fails the head of the piston 22 abuts against the piston 22 to apply direct action. In a further modification the pistons 21, 22 are contained in separate cylinders, connected to a common transmission. In this arrangement a pawl and ratchet may control the movement of the piston to compensate for wear. According to the second Provisional Specification an arrangement comprising two separate hydraulic cylinders is provided with arrangements to charge the hydraulic system when the pedal is operated, the rear of the vacuum-operated hydraulic piston acting as a pump. The cylinder of this piston is surrounded by a container and the hydraulic medium is drawn through a suction valve on the outward stroke of the piston and forced into the system or returned through a relief valve to the container on the return stroke.